Metabolic shifts in glycogen-accumulating organisms: Exploring carbon and phosphorus dynamics under two distinct phosphorus limitation modes

Abstract

Glycogen-accumulating organisms (GAOs) are recognized as competitors of phosphorus-accumulating organisms (PAOs) in enhanced biological phosphorus removal (EBPR) systems. However, different types of GAOs exhibit unique metabolic traits in different environments. To characterize the metabolic activity of GAOs, two distinct modes were constructed. Long-term operation with the mode of anaerobic post-drainage demonstrated the successful establishment of a rapid and enduring GAOs system dominated by Candidatus Contendobacter community. Acetate was completely consumed within 60 min of the anaerobic phase. Concurrently, glycogen levels decreased by 0.062 g Glycogen/g SS, while intracellular carbon storage of poly-hydroxybutyrate (PHB) and poly-hydroxyvalerate (PHV) increased by 0.027 g PHB/g SS and 0.007 g PHV/g SS, respectively. Various concentrations of phosphorus loads illustrated the resistance of the system to high phosphorus loads, while maintaining glycogen accumulating metabolism (GAM). Under complete phosphorus limitation, no correlation between glycogen and acetate was observed during the initial 140 d. The addition of 1 mg/L phosphate to the influent preserved the typical GAM characteristics. Moreover, the pathway involved in glycogen conversion to trehalose may be pivotal in enhancing anaerobic glycogen degradation. The complete tricarboxylic acid cycle ensured efficient energy production, thereby sustaining the foundational metabolism. Notably, sucC and mdh were critical regulators of energy flux. This study provides a distinctive metabolic profile of a robust and resilient GAOs model with Ca. Contendobacter.